That depends entirely on how much you vape. If you are vaping often, you may need to replace your coil on a week by week basis, but for those who are more of a casual vaper, your coils may last longer. Your vape will start to taste either burnt or dull, which is a sign that it will need to be replaced. The type of liquid you use will also affect how long the coil will last, for example using a 50/50 vg/pg liquid in a coil that requires 70/30 vg/pg will affect the life of your coil. Your coils will also have a recommended wattage for use, staying within these parameters will help your coil life.